SCIENCE06L02: The Circulatory System

OBJECTIVES
 Identify the different parts and organs of the circulatory system
 Name and describe the function of the blood and parts of the heart
 Trace the flow of blood from the heart to the different parts of the body
 Enumerate different ailments associated with the circulatory system
 Understand the importance of taking care of the circulatory system
LESSON PREREQUISITE
LESSON PROPER
The Circulatory System
The Circulatory System comprises the blood, blood vessels, and the heart. It
is also called the cardiovascular system, in which “cardio” refers to heart while “vascular” refers to blood vessels. This system transports blood to get oxygen from the lungs and delivers oxygen and nutrients and collects wastes from different body parts. The movement of blood around the body is blood
circulation.
Blood becomes oxygenated every time it passes through the lungs to collect
oxygen and release carbon dioxide. It becomes deoxygenated blood every time it releases oxygen and nutrients to different body parts and collects waste materials like carbon dioxide.
Types of Blood Circulation
This system performs two important blood circulation tasks:
1. Pulmonary circulation is the movement of blood between the heart and
the lungs. In this circulation, deoxygenated blood goes to the lungs to collect
oxygen and release carbon dioxide. It becomes oxygenated blood and flows
back to the heart.
2. Systemic circulation is the movement of blood between the heart and the
rest of the body. In this circulation, oxygenated blood goes to different body
parts to bring oxygen and nutrients. It becomes deoxygenated blood and
collects waste materials like carbon dioxide from the body parts before
returning to the heart.
The Parts of Your Circulatory System
Heart
Lungs
Blood Vessels
BLOOD
The blood delivers nutrients, especially oxygen, to different body parts and
collects their waste materials like carbon dioxide. It also helps in wound healing and protects the body from harmful microbes. The blood needs the help of the heart and the blood vessels so it can flow around the body and do its task.
It is a mixture with 45% solid parts called blood cells and 55% liquid part called plasma.
Plasma
- It is the straw yellow liquid that holds the red blood cells, white blood cells, and platelets together.
Red Blood Cells (or Erythrocytes) - These tiny biconcave and disk-shaped blood cells contain hemoglobin. Hemoglobin helps the red blood cells carry oxygen and gives the blood a red color. The blood has more red blood cells than platelets and white blood cells because of its oxygen-carrying task.
White Blood Cells (or Leukocytes) - These larger blood cells protect the body from diseases by fighting disease-causing microbes. They make antibodies to help them find and identify harmful organisms in the body.
Platelets (or Thrombocytes) - These small and irregularly shaped blood cells help your body heal when you get wounds. It forms a thick and sticky covering of dried blood called a blood clot to stop the blood from flowing out of your body.
BLOOD VESSELS
These are like roads or passageways of blood from the heart to all parts of the body. The system of blood vessels consists of the artery, veins, and
capillaries.
Artery (Arteries, plural)
- It carries blood away from your heart. Aorta is the biggest artery, while
arterioles are the smallest arteries.
- The walls of arteries are thicker and stronger than the veins and
capillaries. It must be strong enough to receive the force of blood from
the heart after each pump. This push force of your blood against the
arterial walls is called blood pressure. Healthy arterial walls also stretch a
bit to allow sudden surges of blood. They also return to their normal size
every after the rush of blood.
Vein (Veins, plural)
- It carries blood toward your heart. Venules are the smallest veins.
Capillary (Capillaries, plural)
- It is the smallest blood vessels connecting the arterioles and venules. Your body parts get nutrients from the blood, like oxygen, and release wastes to the blood, like carbon dioxide, through the capillaries.
In systemic circulation (heart-to-body and vice versa), arteries carry
oxygenated blood while veins carry deoxygenated blood. In pulmonary
circulation (heart-to-lungs and vice versa), arteries carry deoxygenated blood while veins carry oxygenated blood.
HEART
It is a hollow muscular organ, about the size of your fist, that pumps the
blood to the different parts of the body. It is enclosed in a protective sac called pericardium that also keeps your heart in place in your chest. Like other organs, it has its own blood vessels called coronary arteries that deliver nutrients to heart muscles.